It sounds like a wiring fault, it could be the alarm system as there could be a wiring fault and it's draining the battery securing your car over night. another way to test is to removing the car battery when parked up over night and then plug it in the next morning, if it's dead then it's a battery problem, if it's fine then it's a wiring fault. Let me know how it goes.

Parasitic power drains can be hard to trace. Not all alternator tests are 100% .

Have current drain checked with engine and everything off!

Anything over few milliamps is likely our problemPuling fuses on each circuit in turn and checking for flow drop ought to pinpoint the circuit. Decent technician can trace the component fairly easily then.

I'm going thru the same thing....my cable wire running from the alternator - starter burnt in half and they say it might be because the starter wire may have been touching the side. My neighbor cut off the damaged part and inserted a fuse as a temp fix...it's working great...for 6 months before frying the fuse and having to replace it again with another 100 amps fuse.

better to take ur car to the mechanic. dont waste time.

I bought my 2006 civic ex coupe a year ago, and it came with a bad battery, (common for used cars). My car started dying on me as I was driving 2 weeks ago, so I decided to replace the battery and check the alternator. The alternator tested good, amd since then my car has been dying overnight, something is draining it. I got a diagnostics done on the circuits and ground, everything came out good. I also exchanged the battery I first bought because I read online sometimes bad batteries are left to sit on the shelves of stores. What is causing my battery to get drained?

-thank you